Method of stabilization of rubber with a substituted triazine and compositions stabilized thereby



United States Patent 3,240,749 METHOD OF STABILIZATION 0F RUBBER WITH A SUBSTITUTED TRIAZlNE AND COMPOSITIONS STABELIZED THEREBY Martin Dexter, White Plains, Martin Knell, Stillwater Hills, Ossining, and Eric A. Roskin, Bronx, N.Y., assignors to Geigy Chemical Corporation, Ardsley, N .Y., a corporation of Delaware No Drawing. Original application Apr. 11, 1961, Ser. No. 99,663. Divided and this application Oct. 25, 1962, Ser. No. 242,570

4 Claims. (Cl. 26045.8)

This application is a divisional application of copending application Serial No. 99,663, filed April 11, 1961. Application Serial No. 99,663 is in turn a continuation-inpart of copending application Serial No. 21,604, filed on April 12, 1960, now abandoned, and also a continuationin-part of copending application Serial No. 87,521, filed February 21, 1961, now abandoned.

This invention relates to a method of stabilization of rubber with a substituted triazine and to compositions stabilized thereby.

The instant invention contemplates bis-substituted triazines, particularly compounds of the formula:

wherein R' R' R' and R each independently represents alkyl, preferably alkyl having from 1 to 18 carbon atoms, cycloalkyl having from 5 to 6 carbon atoms, aryl, preferably phenyl, substituted aryl, preferably hydroxyphenyl, alkylphenyl, preferably having from 7 to 24 carbon atoms, alkylhydroxyphenyl, preferably having from 7 to 24 carbon atoms, alkylhydroxybenzyl, preferably having from 8 to '15 carbon atoms, cyanoalkyl, preferably cyano-lower alkyl, alkylmercaptoalkyl, preferably having from 2 to 10 carbon atoms, carbalkoxyalkyl, preferably having from 4 to 16 carbon atoms, carbalkoxyaryl, preferably carbalkoxyphenyl having from 8 to 19 carbon atoms,

X X Y Y Z and Z each independently represents 4-, O or NR wherein R is aralkyl, e.g. benzyl, alkyl, e.g. lower alkyl or hydrogen, and

nis 0,1, 2, 3,4, '5 or 6,

m is 0 or 1,

pis 0, 1, 2, 3, 4, 5 or 6, and

X has the same definition as X, hereinabove, are useful for stabilizing rubber.

Patented Mar. 15, 1966 A particularly preferred rubber stabilizer is constituted by a compound of the formula:

I I inS S-Rs wherein R R R and R each independently represents an alkyl group having from 1 to 18 carbon atoms, e.g.

methyl, ethyl, propyl, butyl octyl, dodecyl, octadecyl,

etc.

In this specification, the term lower alkyl signifies an alkyl group having from 1 to 6 carbonatoms, and aryl embraces within its meaning not merely carbocyclic, e.g. phenyl, naphthyl, etc., but also heterocyclic radicals, e.g. pyridyl, thiazolyl, etc.

Up to the present time, the use of the substituted triazines of the invention in stabilizing rubber, e.g. artificial rubber, such as polyisoprene or styrene-butadiene rubber, has not been known. It has now surprisingly been found that such materials are stabilized, e.g. against oxidative deterioration, by incorporating therein effective quantities of one of the substituted triazines defined according to the present invention.

Accordingly, it is a prime object of the invention to provide stable rubber, preferably stable artificial rubber, e.g. polyisoprene. Other examples of rubber stabilized according to the invention include styrene-butadiene rubber, polybutadiene rubber, butyl rubber, nitrile rubber, neoprene rubber and natural rubber alone, blends of articifial rubber and natural rubber, such as e.g. natural rubber and polybutadiene rubber. In fact, any rubber subject to degradation by atmospheric oxygen is wtihin the scope of the present invention. Artificial rubber, however, is preferred.

It is a further object of the invention to provide a method for stabilizing rubber, particularly artificial rubber and blends thereof with natural rubber, by incorporating in said rubber a stabilizing amount of a triazine compound according to the invention.

It is understood that the stabilizers of the invention are not necessarily of equivalent potency. The specific stabilizer most useful to a given unstable rubber will depend upon several factors for its advantages. Availability and cost of raw materials for the manufacture of the stabilizer and effective inhibitory action of the stabilizer, including duration and degree of activity, are among the factors which control the choice of a specific stabilizer for a specific rubber substrate which is normally subject to deterioration. Toxicity, color, stability to light and/ or heat and solubility are also important factors. For example, a preferred composition according to the invention comprises from about 0.001% to about 5% by weight of 6 (4 hydroxy 3,5 di t 'butylanilino) 2,4 bis- (n octylthio) 1,3,5 tria'zine and polyisoprene.

In general, stabilizers of the invention are employed in a concentration of from about 0.001% to about 5% by weight, preferably from about 0.01% to about 1% by weight. The specific concentration used varies with the unstabilized rubber substrate and the specific stabilizer, as noted above. When mixtures of two or more stabilizers are employed in rubber, usually the total amount of added stabilizers will not exceed 10% of the total stabi lized rubber.

When the :triazine stabilizers disclosed herein are used to stabilize rubber in combination with other additive agents, it is contemplated that there may be added, for example, antioxidants, carbon black, accelerators and other chemicals used in rubber compounding, plasticizers, color stabilizers, heat stabilizers, UV absorbers, dyes and pigments, etc.

3 The compounds of the present invention are advantageously prepared, for example, according to the following reactions, wherein R represents the same or different radicals corresponding to R R R and R SIH SIR SiR SIR In the foregoing scheme of reactions, it is understood, that, while cyanuric chloride is -a preferred starting material, other triazine compounds having reactive groups other than halogen may be used.

In the foregoing scheme also, the H of ROH and RSH may be replaced by a suitable reactive group or atom, as e.g. an alkali metal, such as sodium, potassium, etc., or the ammonium radical.

For reaction with a suitable triazine, mercaptans RSH are useful. The R group is advantageously an alkyl group having from 1 to 18 carbon atoms, e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl. R is also advantageously a cycloalkyl group, e.g., cyclophentyl and cyclohexyl. In other aspects R is aryl, e.g., phenyl, hydroxyaryl, e.g. hydroxyphenyl, alkylaryl, e.g., alkylphenyl having from 7 to 24 carbon atoms, such as tolyl, ethylphenyl, propylphenyl, butylphenyl, octylphenyl, octadecylphenyl, etc.; alkylhydroxyaryl, e.g. alkylhydroxyphenyl, such as methylhydroxyphenyl, dimethylhydroxyphenyl, trimethylhydroxyphenyl, tetramethylhydroxyphenyl, ethylhydroxyphenyl, diethylhydroxyphenyl, triethylhydroxyphenyl, tetraethylhydroxyphenyl, propylhydroxyphenyl, dipropylhydroxyphenyl, butylhydroxyphenyl, dibutylhydroxyphenyl, octylhydroxphenyl, dioctylhydroxyphenyl, octadecylhydroxyphenyl, etc.

Another useful class of R groups comprises the alkylthioalkyls, such as methylthiomethyl, methylthioethyl, methylthiopropyl, methylthiobutyl, methylthiopentyl, etc., also ethylthiopentyl, etc., propylthiomethyl, propylthioethyl, propylthiopropyl, propylthiobutyl, propylthiopentyl,

4- etc., butylthiomethyl, butylthioethyl, butylthiopropyl, butylthiobutyl, butylthiopentyl, etc., pentylthiomethyl,

pentylthioethyl, pentylthiopropyl, etc., hexylthiomethyl, hexylthioethyl, hexylthiopropyl, etc., heptylthiomethyl, heptylthioethyl, heptylthiopropyl, octylthiomethyl, octylthioethyl, etc.

Other useful R groups comprise benzyl, hydroxybenzyl and alkylhydroxybenzyl, e.g. methylhydroxybenzyl, ethylhydroxybenzyl,propylhydroxybenzyl, butylhydroxybenzyl, octylhydroxybenzyl, etc.; cyanoalkyl, e.g. cyanomethyl, cyanoethyl, cyanopropyl, cyanobutyl, cyanopentyl, cyanohexyl, etc.; carbalkoxyalkyl, e.g. carbomethoxymethyl, carbethoxyethyl, carbopropoxyethyl, carbododecanoxyethyl, etc.; carbalkoxyphenyl, e.g. carbomethoxyphenyl, carbethoxyphenyl, carbopropoxyphenyl, carbododecanoxyphenyl, etc.

The following examples are illustrative of the invention, but by no means is the invention limited thereto. In all examples parts are by weight unless otherwise noted, and the relationship between parts by weight and parts by volume is as that of grams to cubic centimeters. The temperature is in degrees centigrade.

Example 1 .6-(4-hydr0xy-3,5-di-t-bulylanilino)2,4- bis-(n-octylthio) -1,3,5-tri zine (a) 4-nitr0s0-2,6-di-t-butylphen0l.-75O parts by volume of ethanol, cooled to 15, are saturated with hydrogen chloride gas and then diluted by the addition of 4000 parts by volume of ethanol. 2,6-di-t-butylpheno1 (824 parts) is dissolved in the alcoholic solution and a solution of sodium nitrite (304 parts in 400 parts by volume of Water) is added at 1520 over a period of one hour while stirring. Stirring is continued for another 2 hours While allowing the temperature to rise to room temperature. 2000 parts by volume of water are added and the product is then separated by filtration and washed well with water. The filter cake is slurried in 3000 parts by volume of petroleum ether, filtered, Washed on the filter with 1000 parts by volume of petroleum ether and dried in a vacuum oven at 80. The yield of 4-nitroso-2,6- di-t-butylphenol, melting at 219, is 848 parts (90.2%).

(b) 4 amin0-2,6-di-t-butylphen0l.4-nitroso-2,6-di-tbutylphenol (176 parts) is dissolved in 600 parts by volume of 5 N sodium hydroxide and 1200 parts by volume of water, and a solution of sodium hydrosulfite (522 parts) in 2200 parts by volume of water is added with moderate speed (about 30 minutes), during which time the temperature rises to 53 After the addition is completed, stirring is continued for 2 /2 hours after which the product is filtered rapidly, Washed with 4000 parts by volume of water and dried in a vacuum desiccator over phosphoric anhydride. The yield of 4-amino-2,6-di-t-butylphenol, melting at IDS-108 is 162.3 parts (98.5%).

(c) 6 (4 hydr0xy-3,S-di-t-butylanilino)-2,4-a'ichl0r0- 1,3,5-triazine.A solution of cyanuric chloride (18.4 parts) in boiling acetone parts by volume) is poured in a thin stream while stirring into 200 parts by volume of ice-water, keeping the temperature at 05 with external cooling. 4-amino-2,6-di-t-butylpheno1 (22.1 parts) and sodium carbonate (5.3 part-s) are added and the reaction mixture is stirred vigorously at 8-10 for 45 minutes. The mixture is then diluted by the addition of 100 parts by volume of acetone and stirring is continued for an additional hour at 8-10. The suspension is then poured into 500 parts by volume of ice-Water, the precipitate is filtered OE and dried in vacuo. The yield of 6 (4 hydroxy-3,S-di-t-butylanilino)-2,4-dichloro-1,3,5- triazine is 34.8 parts (94% The product melts at 144.

(d) 6 (4 hydroxy 3,5-di-t-butylanilin0)-2,4-bis-(nactylthio)-1,3,5-triazine.An alcoholic solution of sodium n-octylmercaptide (prepared by dissolving 2.3 parts of sodium in 50 parts by volume of ethanol and adding 14.6 parts of n-octylmercaptan) is added rapidly with stirring to a solution of 18.5 parts of 6-(4-hydroxy-3,5-dit-butylanilino)-2,4-dichloro-1,3,5-triazine in 150 parts by volume of ethanol. refluxed for 1 hours. After cooling to room temperature, 500 parts by volume of Water are added. The precipitated product is separated by filtration and washed well with water. Purification of the product is accomplished by dissolving in 300 parts by volume of boiling ethanol, adding activated carbon, filtering and slowly recrystallizing. The 6 (4-hydroxy-3,S-di-t-butylanilino)- 2,4-bis(n-octylthio)-l,3,5-triazine, which crystallizes as white needles, is filtered off, washed with cold ethanol and is dried in vacuo yielding 10.6 parts melting at 92-95". Additional 8.6 parts having the same melting point are obtained by concentration of the mother liquor. The total yield is 65.5% of the theoretical yield.

Example 2.6-(4-hydroxy-3,5-di-t-butylphen0xy)-2,4-bis- (n-octylthio) -1,3,5-triazine An alcoholic solution of sodium 4-hydroxy-3,5-di-tbutylphenoxide [prepared by dissolving 60 parts of sodium in 5000 parts by volume of ethanol and adding 666 parts of 2,6-di-t-butylhydroquinone (US. Patent No. 2,927,- 932)] is added rapidly while stirring to a solution of 1212 parts of 2,4-bis-(n-octylthio)-6-chloro-1,3,5-triazine in 2500 parts by volume of ethanol. After the exothermic reaction subsides, the reaction mixture is allowed to stand several hours before removing the salt by filtration. The filtrate is treated with activated carbon, filtered, and the filtrate is concentrated to dryness under vacuum. The oily residue therefrom is dissolved in hexane, adsorbed on a silica gel column and eluted with 50% benzene/hexane. After evaporation of the solvent therefrom the 6-(4- hydroxy 3,5 di-t-butylphenoxy) 2,4-bis-(n-octylthio)- 1,3,5-triazine is obtained as a light colored viscous oil in 67% yield.

Analysis.Calculated for C H O N S C, 67.19%; H, 9.4%; N, 7.12%. Found: C, 66.84%; H, 9.11%; N, 7.26%.

By replacing 2,6-di-t-butylhydroquinone with hydroquinone, the chromatographic separation is unnecessary, since the crude reaction product is precipitated by the addition of water. Fractional crystallization from ethanol separates two products, which are obtained in 21.5 and 15.4% yields, respectively. Said products are, respectively:

1,4 phenylene bis-[2-oxy-4,6-bis-(n-octylthio) ]-1,3,5- triazine; M.P. 98 (recrystl. from ethanol);

6 (4-hydroxyphenoxy)-2,4-bis-(n-octylthio)-1,3,5-tria zine; M.P. 79-80.

Example 3.

Stabilized rubber is prepared by mixing in the cold:

Parts Hevea latex crepe 100.0 Stearic acid 1.5

The reaction mixture is stirred and p Parts Zinc oxide 5.0 Diphenylguanidine 1.0 Sulfur 2.5 6 (4 hydroxy 3,5-di-t-butyl-anilino)-2,4-bis-(noctylthio)-l,3,5-triazine 1.0

The resultant mixture is vulcanized at and tested according to ASTM D120652T. The time required to elongate a test strip from 120 mm. to mm. is 10 hours for the unstabilized rubber and 17 hours for the stabilized rubber. In a similar way, styrene-butadiene rubber is stabilized. In a similar way also, a blend of natural rubber (50 parts) and polybutadiene rubber (50 parts) is stabilized.

In like manner as in the foregoing Example 3, stable compositions of natural rubber are prepared having 0.9% by weight of the following compounds: 6-(4-hydroxy-3,5-di-t-butylphenoxy) -2,4-bis- (noctylthio)-1,3,5-triazine 1,4-phenylene-bis-[2-oxy-4,6-bis-(n-octylthio) -1,3,5-

triazine] 6- (4-hydroxyphenoxy) -2,4-bis- (n-octylthio -l ,3,5-triazine What is claimed is:

1. Method of stabilizing rubber selected from the group consisting of conjugated diene rubber, butyl rubber, and nitrile rubber which comprises incorporating therein a stabilizing amount of a stabilizer, said stabilizer being a compound of the formula:

11S( m lSRs N N N N K RID-S S a wherein R R R and R are each independently an alkyl radical, having from 1 to 18 carbon atoms.

2. Stabilized composition of matter which comprises rubber selected from the group consisting of conjugated diene rubber, butyl rubber, and nitrile rubber and a stabilizing amount of a stabilizer as defined in claim 1.

3. Stabilized composition of matter which comprises rubber selected from the group consisting of conjugated diene rubber, butyl rubber, and nitrile rubber and from about 0.001% to about 5% by weight of a stabilizer as defined in claim 1.

4. Stabilized composition of matter which comprises rubber selected from the group consisting of conjugated diene rubber, butyl rubber, and nitrile rubber and from about 0.001% to about 5% by weight of 1,4-phenylenebis- [2-oxy-4,6-bis- (n-oc-tylthio) -1,3,5-triazine.

No references cited.

LEON J. BERCOVIT Z, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3, 240, "49 March 15, 1966 Martin Dexter et al It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

within column 3,

Column 2 line 5 tor "wtih in" re ad shown lines 5 to 10, the right hand formula should appear as as in the patent;

Cl L N SR strike out the formulas below instead or same column 3, lines ll to Z2,

Signed and sealed this lst day of August 196 (SEAL) Attest:

EDWARD M1 FLETCHER, JR EDWARD J BRENNER Attesting Officer Commissioner of Patents 

1. METHOD OF STABILIZING RUBBER SELECTED FROM THE GROUP CONSISTING OF CONJUGATED DIENE RUBBER, BUTYL RUBBER, AND NITRILE RUBBER WHICH COMPRISES INCORPORATING THEREIN A STABILIZING AMOUNT OF A STABILIZER, SAID STABILIZER BEING A COMPOUND OF THE FORMULA: 